Composition containing polyethylene and a polypropylene glycol monoalkyl ether



United States Patent COMPOSITION CONTAINING POLYETHYLENE AND A POLYPROPYLENE GLYCOL MONO- ALKYL ETHER James D.. Engle, Torrance, Califi, assignor to Union Carbide Corporation, a corporation of New Yorkv No. Drawing. Filed Nov. 20,1956, Ser. No. 623,511 7 Claims. (Cl. 26014-333) ployed to stabilize the Conventional polyethylene films have poor slip behavior and consequently their use in automatic processing equipment presents something of a problem; since the film must pass freely throughthe fabricating machine for proper and reproducible operation. A convenient measure of a films slip behavior is its coefiicientof friction as determined'by the moving sled stationary film method subsequently described. Different specimens of film heretofore available have coeflicients of friction ranging from about 0.4 to about 0.9, with a high percentage of the values falling above 0.6.

It has now been found that the addition to a normally solid polyolefin of from about 0.005% to about 0.5% by weight of a polypropylene glycol monoalkyl ether having an average molecular weight of from about 750 to about 3000, wherein the alkyl group may contain up to about 6 carbon atoms and preferably 3 or 4 carbon atoms, improves the slip behavior of the pol-yolefin. The slip agents suitable as lubricants in this invention may be represented by the following general formula:

wherein x represents an integer having a value of from 0 to about 6 and n represents an integer having a value of from about 12 to about 52. Among the polypropylene glycol monoalkyl ethers suitable for use in this invention are the methyl, ethyl, propyl, butyI, pentyl and hexyl ethers.

The polypropylene glycol monoalkyl ethers. suitable in this invention are those having average molecular weights from about, 750 to about 3000;: preferably from about 1000 to about 1750, with the most preferred molecular weights being from about 1200 to about 1500. The presence of small amounts, up to. about 5% by weight,'of inhibitors such as phenyl alpha. naphthylamine; in. the lubricant can be tolerated without causing any appreciable deleterious effects on the properties of the film."

The amount of lubricant. added to. the polyethylene may be varied from about. 0.005%. to. about 0.5% by weight of the polyethylene. Preferably from about 0.01 to about 0.1% by weight of lubricant is added, with the most preferred amount ranging from about 0.025% to about 0.05% by weight.

The lubricant may be added to the normally solid polyethylene by any suitable means. For example, it may be added after the polyethylene has. been producedto the pelleted or powdered polymer such as by tumbling or spraying; or it may be added to the ethylene feed prior to polymerization thereof. It has been found that this latter technique is preferred since better contact of lubricant with polymer can be achieved. It has also been established by infrared studies of polymer samples produced with lubricant added to the ethylene feed that the lubricant does not react with the ethylene during the polymerizationbut is simpl-yentrained per se in the finished polymer.

Concentrations of ether of about 0.04%

haze, glass, fish-eye. rating, appearance, impact strength, drawdown thickness, and. drawdown speed. At concentrations above about 0.2%. by weight the surface of the film tends to become oily and this may cause blocking difliculties. By blocking is meant that two films sepae rated by a; thin layer of oil are held firmly together by cohesive forces and thus require excess perpendicular forces for separation.

In addition to. the lubricants herein described the polyethylene may also contain other additives normally empolymer against heat and light degradation, or to color the polymer.

The moving sled stationary film method for determining-the coefficient offriction is as follows:

A 16" x 18" sampleof film is taped smoothly to'the surface, of a level plane with the machine direction of the film. in the direction. of sled travel. Care is taken to remove all wrinkles without causing any elongation of the, film. A smaller specimen of the film is attached to a sled consisting of a steel block /8 x 2% x 4" mounted on a rubber base which has a total weight of one kilo.- gram. The sled is attached to a synchronous motor by means. of a tow line with the tow line passing through a gage which in turn is connected to afmicroammeter in which the microammeter scale has been replaced with a coefficient of friction scale reading from 0 to l, with I corresponding to a full scale reading of the meter: (30 microamps). The film-covered sled is placed on the level plane and pulled by the motor. The coefficient of friction is read directly from the scale after the sled has traveled 1, 2 and 3 inches and the average of these three values is taken. The test is then repeated with another two small specimensof the film on the sled and the average taken for the three test specimens examined is reported as the coefficient of friction.

The following examples further serve to illustrate the invention.

Example 1 Ethylene, containing about 75 parts per million. by volume of oxygen, was compressed to about 32,000 p.s.i. During the compression, when the pressure was about 2000 p.s.i., polypropylene glycol monobutyl ether having an average molecular Weight of about 1200 was added to the ethylene to give a concentration of about 49.- partsper million of the glycol ether lubricant in the ethylene. This.

mixture was passed through a jacketed tubular reactor about 460 feet long having an inside diameter of about one-half inch at a rate of about 1800 pounds per hour and at a reactor temperature of 240 C. and a reactor pressure of about 32,000 p.s.i. After passing through the reactor the liquid polymer and unreacted ethylene were discharged intermittently through a'suitable controi valve to a heated separating vessel where the polymer.

was separated fromthe unreaoted' ethylene which was recovered and recycled. The molten polymer was ex traded into water'to cool and solidify and recovered,

therefrom; The resin had a melt index'of'lAdgm/in" (A.S.T.M. D-1'238 52T) and a'dens'ity of'0L9175 gram/ cc. (Hunter and to the ethylene feed had a coefficient of friction of 0.7.

This control sample had a melt index of 2.0 dg'nL/min, and a density of 0.9190 gram/cc.

polypropylene glycol monobutyl by weight in. polyethylene served to reduce. the coefiicientof friction about 40% or greater 5 without significantly influencing other properties such as Oaks, Tran's.'Far. Soc. 41; 49 rne polymer was then extruded as a flat film 1.5 mils thick. The coefficient of friction determined by the moving sled I What is claimed is:

1. A homogeneous composition of matter consisting essentially of a normally solid polyethylene and from about 0.005% to about 0.5% by weight of the polyethylene of a polypropylene glycol monoalltyl ether represented by the general formula':

CHI oHiwImxowmHohH wherein .1: represents an integer having a value of from 0 to about 6 and n represents an integer having a value of from about 12 to about 52.

2. A homogeneous composition of matter consisting essentially of a normally solid polyethylene and from about 0.01% to about 0.1% by weight of the polyethylene of a polypropylene glycol monoalkyl ether represented by the following general formula:

wherein x represents an integer having a value of from 0 to about 6 and n represents an integer having a value of from about 12 to about 52.

3. A homogeneous composition of 'matter consisting essentially of a normally solid polyethylene and from about 0.005% to about 0.5% by weight of the polyethylene ot a polypropylene glycol monobutyl ether, said ether having a molecular weight of from about 750 to about 3000.

4. A homogeneous composition of matter consisting essentially of a normally solid polyethylene and from about 0.01% to about 0.1% by weight of the polyethylene of a polypropylene glycol monobutyl ether having an average molecular weight of from about 750 to about 3000.

5. A homogeneous composition of matter consisting essentially of a normally solid polyethylene and from about 0.01% to about 0.1% by weight of the polyethyl- References Cited in the file of this patent UNITED STATES PATENTS Run- A 'B Lubricant, p.p.rn 119 368 Coetficient of friction 0.23 0.20 Melt index, dgm./min 1. 7 2. 2 Density, g./cc 0. 9164 Example 2 Ethylene was polymerized in the same manner as described in Example 1 using a polypropylene glycol monobutyl ether having an average molecular weight of about 2500 as lubricant. The results are summarized below:

'Rnn v CO lIlOl A B Lubricant, p.p.m 0 780 1,560 Coetiicient of friction. 0. 70 0. 60 0. 51 Melt index, dgmJmin 2. 0 2.0 1.4 Density, g./cc 0.9190 0.9170 0.9154

Example 3 Ethylene was polymerized in the same manner as described in Example 1 using a polypropylene glycol mono butyl ether having an average molecular weight of about 1200 and containing therein about 2 percent phenyl alpha naphthylamine therein as inhibitor. The results are summarized below:

Run Control A B O D Reactor temperature, 0. 240 230 230 195 195 Lubricant, p.p.m 0 775 1,550 775 1, 550 Ooeiileient of friction. 0.70 0.16 0.16 0.35 0.38 Melt index, dgm./min- 2. 0 2. 8 1.8 l. 7 2. 5 Density, g./cc 0. 9190 0. 9174 0.9176 0. 9196 0.9190

Example 4 Polyethylene having a melt index of about 2 dgm./ min. and a density of about 0.917 g./cc. was extruded to form pellets of about /8 inch diameter. The pellets were then treated in a double-cone blender with various amounts of polypropylene glycol monobutyl ether having an average molecular weight of about 1200. The lubricant-containing pellets were then extruded in a flat film extruder to produce film about 1.5 mils thick. Results are summarized below: 1

Run Control A B 0 D .E

Lubricant, p.p.m 0 so 200 400 1,000 Coetlicient of friction 0.47 0.42 0.35 0.30 0.27 .25

Example.5 Polyethylene pellets as described in Example 4 were sprayed with various amounts of polypropylene glycol monobutyl ether having an average molecular weight of about 1200. The pellets were then extruded in a flat film extruder to produce film about 1.5 mils thick. Results are summarized below:

Run- A n Lubr1cant,pp 400 4,000 Coeflleient of friction 0.40 .23

2,293,868 Toussaint Aug. 25, 1942 2,353,228 Ducca July 11, 1944 2,448,664 Fife et a1. Sept. 7, 1948 2,510,540 Ballard June 6, 1950 2,519,013 Banigan Aug. 15, 1950 2,520,733 Morris Aug. 29, 1950 2,579,375 Eisen Dec. 18, 1951 2,668,801 Schultz Feb. 9, 1954 2,718,509 Lundsted et al. Sept. 20, 1955 2,728,755 Weisemann Dec. 27, 1955 FOREIGN PATENTS Great Britain May 5, 1948 

1. A HOMOGENEOUS COMPOSITION OF MATTER CONSISTING ESSENTIALLY OF A NORMALLY SOLID POLYETHYLENE AND FROM ABOUT 0.005% TO ABOUT 0.5% BY WEIGHT OF THE POLYETHYLENE OF A POLYPROPYLENE GLYCOL MONOALKYL ETHER REPREPRESENTED BY THE GENERAL FORMULA: 